Heat exchangers to be mounted in automobiles are formed by assembling components shaped from brazing sheets and brazing the assembled components, which brazing sheets each include an aluminum alloy core material clad with a filler material. Gauge down of such aluminum alloy brazing sheets for heat exchangers, typically for tube members, have been proceeded from a customary thickness of 0.3-0.5 mm to 0.2 mm or less for the purpose of weight reduction of the heat exchangers. Along with this, the aluminum alloy brazing sheets should have higher strength and better corrosion resistance. The weight reduction of a heat exchanger may be possible by employing a tube member composed of the aluminum alloy brazing sheet having a filler material facing outward, in combination with a fin member (bare fin) containing no filler material. This heat exchanger, however, is difficult to exhibit sufficient corrosion resistance when the filler-clad surface of the tube member, which is clad with the filler material to be joined with the fin member, is exposed to a corrosive environment.
To solve the problem, Patent Literature (PTL) 1 discloses an aluminum alloy brazing sheet which includes a core material and, present thereon, a filler material, which core material is composed of an Al—Mn alloy, and which filler material is composed of an Al—Si alloy containing Si in a content of 7.0 to 11.0 percent by mass and further containing Zn in a content of 1.0 to 7.0 percent by mass. The aluminum alloy brazing sheet is intended to improve its corrosion resistance by allowing part of Zn in the filler material to migrate into the surface layer of the core material during a brazing process and thereby allowing the surface of the component after brazing to have a less novel potential to impart a sacrificial effect to the component.    PTL 1: Japanese Unexamined Patent Application Publication (JP-A) No. H07-331372 (claims 1 and 2, paragraphs 0005, 0009, and 0010)